Electric elevator system



June 14, 1927, 1,632,225

G. B. GROSVENOR ELECTRIC ELEVATOR SYSTEM Filed May 23, 1922 4Sheets-Sheet l INVEETQR June 14,1927. 7 r 1,632,225

G. B- GROSVENOR ELECTRIC ELEVATOR SYSTEM Filed May 23, 1922 4;Sheets-Sheet. 2

% iNVENTOR June 14,1927. 1,632,225

G. B. GROSVENOR ELECTRIC ELEVATOR SYSTEM Filed May 25, 1922 4Sheets-Sheet 3 INVENTOR Agra m un 4 1927. e 1 G. B. GROSVENOR ELECTRICELEVATOR SYSTEM Patented June 14, 1927 UNITED STATES PATENT OFFIQE.

GRAHAM B. GROSVENOR, OF CHICAGO, ILLINOIS, ASSIGNOR TO OTIS ELEVATORCOM- PANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

ELECTRIC ELEVATOR SYSTEM.

Application filed my 23, 1922.v Serial No. 563,094.-

I and retardation was accomplished automatically by means controlled bythe operator. Later automatic means for levelling the floor of theelevator even with the landings" in .stopping were applied. In certainof the 1 most successful elevator systems of the present day, theoperator may run the elevator at a plurality of approximately fixedspeeds,

but in ordinary operation he will move the car switch to full speedposition on startingv up and willavail himself of the automatic controlof acceleration. In stopping he will bring the car switch to the"neutral position at a distance from the landing corresponding to thatwhich he has found by experience 2 will bring the car to rest by-theautomatic retarding means within the zone, of action of, the levellingdevices.

The distance from the landing at which the operator must initiate theautomatic stopping in order to reach the landin in the least possibletime is variable and depends on the speed of the elevatorand the load,as well as on the particular means for retarding the elevator. Hence, insystems of the above type the skill of the operator is an importantfactor in securing a high average speed of the elevator.

- The highestpossible average speed will be obtained when the elevatoris started at the maximum permissibleacceleration, run at full speed,and then stopped with maximum permissible retardation so as to bring thefloor of the car level with the landing. This may be regarded as a goaltoward which elevator systems have striven.

()ne object of my present invention is to provide an automaticslow-down, which will come into action at varying distances from thelanding, to automatically bring the ele-' vator from the speed'at whichit is moving toa definite low speed. The distance from the landing atwhich the automatic slow: down device comes into operationisproportioned to the speed of the elevator so that in such a manner that,by the action of devices suitably located in the hatchway to out offthe. power and apply the brake ata fixed distance from the landing, theelevator will always come to rest approximately level with the landing.Other objects will appear from the detailed description.

To accomplish the first of these objects, 'I may, for example, use apair of strips arranged to move in accordance with the move ments of theelevator, but on a reduced scale. Suitable contacts are provided in thestrips and stationary brushes corresponding with the landings arearranged to contact with the strips. A governor, provided with aplurality of pairs of contacts adapted to be closed successively as thespeed of the governor increases, is driven by the elevator mechanism.These pairs of contacts are each connected in series with a'contact inone of the strips and under proper conditions controlthe full speedoperation of the elevator. Thus, as the elevator approaches a landing,when the controller is in the proper position for automatic slow-down, acircuit is com leted throu 'h those particular contacts of t e strip andovernor that correspond to the position and speed of the car.

The second object is attained, for example, by usinga motor-generator tosupply current to the elevator motor and so designing the generator thatits voltage will be greater when the elevator motor islifting a load(whether in car or in counterweight) than when it is lowering it. Inthis way the speed of the elevator may be higher when the elevator isascending loaded or descending light than it is when the elevatorisascending. light or descending loaded. Then by taking advantage of thefact that. the greater the load the elevator motor is lifting, theshorter the distance required to stop, and coordinating this with thespeed characteristics as described above, the elevatorwill be brought torest in substantially the same distance under allconditions'ofloading.

-In 1n copendingapplication Serial No;

541,815, tiled March" 7th,,1922, I have decable to other elevatorsystems.

In order that my invention may be fully understood, it will be describedby way of example in connection with the accompanying drawings, in whichFigure 1 is a schematic view showing the general arrangement of theapparatus of a system embodying my automatic slow-down and stop.

Figure 2 is a wiring diagram illustratin the action of my automaticslow-down and stop in connection with the system according to myapplication Serial No. 541,815.

Figure 3 is a longitudinal section of my automatic slow-down controller.

Figure 4 is a development of the cylindrical surface of the controllerof Figure 3, showing the contacts and strips Figure 5 is a verticalcross-section of the car switch used by the operator in the elevator tocontrol its movements.

Referring more particularly to the drawings, the motor 4, Figure 1,operates from the supply mains and drives generator 5 through shaft 6.Generator 5 is separately excited and a resistance 7 is included in itsfield circuit. Motor 4 and generator -5 are kept running during suchperiods as the elevator is in service. series field 8 for generator 5 isconnected in the circuit lead ing to the reversing switch 9, from thearmature terminals of generator 5. Elevator niotor 10 is supplied withcurrent for its arma ture through reversing switch 9, whereas-its fieldis separately excited. On an extension of the shaft of elevator motor 10is mounted sheave 11 over which runs the supporting cable 12 of elevator13 and counterweight 14. Brake drum 15 of electro-mechanical brake 16 isalso fastened on the extension of the shaft of motor 10. Brake 16 is soconstructed that when the solenoid 115 is not energized, the shoe 20 isheld against the drum 15 by spring 21 and the elevatormotor 10 isbrought to rest if moving, or held stationar if at rest. WVhen solenoid115 is energize spring 21 is compressed and the brake released Theautomatic slow-down controller 18 is shown as being driven by gear 19from gear 17 which is mounted on the extension of the,

shaft of motor 10. The gears 17 and 19 are selected to give a reductionof motion "to the slow-down controller that will cause its total travelto correspond to the total'travel of the elevator. Controller 18 may bedriven by any other means such as are commonly employed for operatingfloor controllers. Such drives comprise as an essential element meansfor rectifying errors in the required fixed relation between the motionof the controller and of the car, due to slip or creepage of the cable.-One well known means of accomplishing this is indicated at 29 where gear17 is driven by friction produced by the pressure of spring 30. Thecontroller 18 is so-constructed that it can travel only the distancecorresponding to the full travel of the elevator between the upper andlower landings. Consequently any errors due to slip or creepage will becorrected at the ends of each trip of the elevator.

At some suitable point, preferably at the top of the hatchway, islocated a governor 22, which runs-at a speed corresponding to the speedof the elevator. It is here shown as a centifugal governor driven bycable 23 which is attached at both ends to the elevator 13 and runs oversheaves 24, 25, 26 and 27. The function of governor 22 is to closecontacts in the circuit of the slow-down device 18, as will be describedhereinafter. Governor 22 may be the usual governor which serves toactuate the safety devices for stopping the elevator in case of0verspeed.

Automatic stopping switch 28 serves to bring the car to rest from lowspeed approximately level with the landing. It is here shown as asolenoid-operated switch in which the solenoid is mounted at a suitablepoint on the elevator car, whereas the armature 31 is mounted at a pointin the hatchway in such relation that when the elevator floor is levelwith the landing, the armature 31 is opposite the cooperating part ofthe solenoid core.

Car switch 32 is mounted in the elevator car within easy reach of theoperator.

Referring to Figure 2, the shunt motor 4 is connected tothe mains 33, 34through the usual starting box 160. Motor 4 is of the constant speedtype and drives the armature 35 of the generator 5 as described inconnection with Figure 1. The field coil 36 of generator 5 is connectedin series with the resistance 37 across mains 33, 34 by wires 38 and 39.

Field coil 40 of elevator motor 10 is connected through resistance 41 tomains 33, 34 by wires 42 and 43.

A control panel 44 is located at a suitable point, preferably in themotor room, and all the motor circuit closing switches are mounttoo edon it. These switches are solenoid-operis determined by adjusting theresistance 37'. a

If the handle 45 of the car switch 32' be moved in the up direction U,so that com tact 46 covers contacts 47 and 48, a circuit will'be closedfrom main 34 through wires 39, 49, 50, contacts 47, 46, 48, wires 51,52, solenoid winding 53 of magnetic stopping switch 28, wire 54,contacts 55, 56 and wires 57, 38 to main liy energizing solenoid 53 itscore is attracted by the armature 31 and contacts 58, 59 and 60, 61 areopened. Stopping switch 28 may be constructed in various ways toaccomplish this result. 1 have shown it as having, for example, a core62 pivotally mounted at its lower-end on the frame 63 which is attachedto the elevator car. An arm 64 extends from core 62 toward .the ironarmature 31 which is fixed in the hatchway. Stop 65 prevents the arm 64from coming into contact with armature 31 when solenoid 53 is energizedand spring 66 moves core 62 away from armature 31 to close contacts 58,59 and 60, 61 when solenoid 53 is deenergized. Contacts 59 and 61 areinsulated'from each other and from core 62 to which they are attached.

By a further movement of handle 45, whereby contacts 47, 48 and 67 arecovered by contact 46, an open circuit is set (to be closed, as will bedescribed later) from main 34 through wires 39, 49, 50, contacts 47, 46

and 67, resistance 68,'wire 69, contacts 60, 61

(which however are open, due to the action of the stopping switch aslast described) wire 70, solenoid winding 71 and wires 72, 73 and 42 tomain 33.

Still further movement of handle 45 to cover contact 74 by contact 46results in setting a circuit from main 34 through wires 39, 49 and 50,contacts47, 46 and 74, wire 75, resistance 76, wire 77, solenoid winding'78, wires 79 and 80,- resistance 81, contacts 82,

83, wires 84and 85, contacts 86, 87 of the Y direction switch (which arestill open) and wire 38 to main 33. At the same time a circuit is setfrom main 34 through wires 39, 49 and 50, contacts 47, 46 and 74, wire75, resistance 88, wire 89, solenoid coil 90, wires 91 and 92, contact93, bridge contact 94, insulating block 252, strip 95 of the .=low downcontroller, brush 272, wire 96, contacts 97, 9 which are adapted toclose at the same time as the direction switch, and wires 99, 72, 73 and42 to main 33.

' Still further movement of handle 45 to cover contact by contact 46closes a circuit from main 34 through wires 39, 49 and 50, contacts47,46, 100, wires 101, 102 and 70, solenoid winding 71 of the directionswitch, and wifes 72, 73 and 42 to main 33. The closing of this circuitenergizes winding 71 and closes contacts 86, 87 and contacts 103, 104 ofthe direction switch which is of auv usual form of-solenoid-operatedswitch that is held closed when-its solenoid is energized and opened forexample by gravity when the solenoid is deenergized; A circuit nowextends from the armature 35 of genercontacts 87, 86, wires 85 and 34,contacts 83,

82, resistance 81, wires 80, and 111, contacts 112, 113. wire 114,winding of clertroniechauical brake l6 and wire 43 to main 34. Theenergizing of winding 115 releases the electromechanical brake 16 andthe elevator now starts in the up direction at low speed. lVhen thebrake is entirely released, contacts'112, 113 open; (see Figure 1) landresistance 151 is no longer short-circuited. Resistance 151 is soselected that when it. is in the circuit of the solenoid, the currentwill be reduced to a minimum required to hold the brake elf. Thisresults in a saving of power since the full current is flowing throughthe solenoid circuit only at starting. Simultaneously with the closingof the up direction switch, contacts 116, 117 are closed and resistance41 in series with the field winding 40 of elevator motor 10 isshortcircuited through wire 161, contacts 116,117, wires 118, 119,branch circuits through contacts 120, 121 and contacts 122, 123, andwire 73. This gives full field strength for elevator inotor 10 instarting up, hence maximum starting torque. The act of closing the updirection switch simultaneously opens, contacts 124, 125 therebydisconnecting resistance 81 from across the tern'iinal. of armature 400of elevator motor-10. It is to be observed that the circuit trom'the carswitch through winding 78 has now been closed by the closing of thedirection switch and solenoid winding 78 is energized, Due to theresistance 76 in its circuit, however, it does not close contacts 126,127 and contacts 128, 129 of the high speed switch since resistance 1'6is so adjusted that it will not pass sufficient current to close thehigh speed switch but will allow suflicient current to pass through thesolenoid, to hold the latter closed if it has been previously closed.

Still further movement of car switch handle 45 to cover contact 130 bycontact 46 short circuits resistance 76 through wires 131 and 132,and'soleno-id winding 78 of the high speed switch is fully energized.Contacts 126, 127 are thereby closed and restance 37 in the fieldcircuit of generator 5 is short circuited through wire 134, contacts12". 126 and wires 133 and 38. The voltage at the terminals oi generator5 will then increase at a rate dependent on the design of the generatorand elevator motor 10 will increase in speed. Simultaneously with theclosing of contacts 128. 129 and 1:26, 127 of the high speed switch,contacts 122. 123 are opened. Contacts 55, 56 are also opened,

lit)

thereby deenergizing the winding 53 of the stopping switch'28.

W en the voltage at the terminals of generator 5 has built up to acertain percentage (generally about 50%) of the normal full voltage,solenoid 135-is sutliciently energized to open. contacts 120, 121. Sincecontacts 122, 123 have been previously opened by high speed switchsolenoid 78, the short circuit across resistance 41 in the field circuitof elevator motor 10 is opened and elevator motor 10 will have a weakerfield which will cause it to speed up. The voltage at which resistance41 is inserted in the field circuit of elevator motor 10 may be adjustedby changing resistance 136. It is to be noted that re-' sistance 136 andsolenoid winding 135 are connected across the terminals of armature isnow from main 33 through wires 38, 105,.

35 of generator 5 through wires 137, 138 and 139, 38.

When the voltage at the terminals of generator 5 has built up to acertain percentage (generally about 75%) of the normal full voltagesolenoid 140 is sufiiciently energized to close contacts 108, 141 andcontacts 142, 143. The voltage at which this takes place may be governedby changing the resistance 162 in the circuit of solenoid winding 140.This results in placing both generator 5 and elevator motor 10 directlyacross the mains 33, 34. The armature circuit of generator 5 arn'i'ature35, wire 137 contacts 142, 143 and wire 39 to main 34. Series field 8 isshortcircuited in order that driving motor 4 and generator 5, which isnow running as a motor, may have similar characteristics for paralleloperation. This is advisable because motor 4 and genera-tor 5 aremechanically coupled. The armature circuit of elevator motor 10 is nowfrom main 33 through wire 38, contacts 87, 86, wire 85, armature 400,

Wire 105, contacts 104, 103, wires 106, 107,-

. contacts 108,141, and wire 39 to main 34.

Thus the elevator motor 10 is being supplied with current directly fromthe mains 33, 34. This is advantageous in that whenever the elevator isrunning .at full speed, power consumption is kept to a minimum since thegenerator 5 and .motor 4 will only require that amount of. powernecessary to turn them over.

Having described the circuits as they are successively closed inbringing the car switch to the'fullspeedup position, I will brieflydescribe the action in moving the car switch handle back to neutral(neglecting the control by the automaticslow-down controller and stop,which will be described. later).

By moving handle 45 back to uncover contact 130 of the car switch 32 theelevator will still run at full speed since solenoid 78 ot' the highspeed w tch is still suflicientlv cnergizcd to hold the switch closed.Moving handle 45 to uncover contact 100 will result in no ch-ange sincethe direction switch is still held inby solenoid 71 by the circuitthrough the contacts 60, 61 of themagnetic stopping switch 28.Resistance '68 inthis circuit is so I thereupoi'i opens. Armature 400 ofelevator motor 10 is then connected across armature 35 of generator 5and the field of elevator motor 10 is restored to full strength. At thesame time, the circuit short-circuiting resistance 37 in the hold ofgenerator 5 is opened and the voltage at the terminals of armature 35drops. Since the elevator is running at full speed the generator willact as a dynam ic brake for the elevator motor and will slow it downuntil its voltage corresponds to the low voltage delivered by thegenerator. By uncovering contact 67 the circuit through resistance 68,contacts 60, 61 and solenoid 71 of the direction switch is opened andthe solenoid dcenergized. The direction switch opens and the elevatorcomes to rest through the dynamic braking action of resistance 81 Ywhich is connected across the armature terminals of elevator motor 10 bythe closing of contacts 124, 125. Resistance 81 may be made very low sothat a strong brakin action is applied. The opening of the irectionswitch also opens the circuit through the electromechanical brake 16 andallows it to act to assist in bringing the elevator to rest and to holdit stationary when it has stopped. It is to be noted that resistance 150is shunted across the solenoid winding 115 of brake 16. This resistanceserves to discharge the solenoid winding 115 when it is disconnectedfrom its supply of current and by selecting the proper resistance thetime required for full application of the brake can be governed. Furthermovement of handle 45 of the car switch to uncover contact 48 opens thecircuit through solenoid 53 of the magnetic stopping switch and finallyuncovering contact 47 opens the circuit from the main 34 to contact 46on the car switch handle.

Although I have described the circuits set or closed as the car switchmovable contact- 46 covers each contact, it is not intended that theoperator will avail himself of all the contacts in the ordinaryoperation of the elevator. By means of my" automatic slow-down and stopin connection with other features of my system, the operator is enabledto normally control the elevator by moving the car switch handle to oneof three positions which I have designated as 1-, 2 and 3 (Figures 1 and2).

Position 1 isneutral and there is no electrical connection to contact 46of the car switch handle 45. Handle 45 is self-centermamas ing and tendsto return to the neutral position whenever the operator removes hishand. This may be accomplished by the torsionspring 200 (Figure 5) oneend of which is fastened to an enlargement 201 of the shaft 202 and theother end to the car switch body. When in the neutral position thespring has no tension. To move the handle in either the up or downdirection it is necessary for the operator to move the grip 203lengthwise in order to disengage the latch 204 from the notch 205. Grip203 is slidably mounted on tube 206 which is securely screwed intohandle 45. An enlargement 207 on latch 204 serves to attach it to grip203. A compression spring 208 is mounted over tube 206, an enlargementof which serves as an abutment for the spring which at all times willtend to engage the latch.

Assuming normal operation in which it is desired to bring the elevatorfrom one landing to another landing above it in the shortest time, theoperator will release the latch 204 by sliding grip 203 longitudinallyand move the car switch handle 45 to its extreme position (position 3)in the up direction so that the latch 204 will rest against the edge 209of notch 210 (Figure 1). All contacts for up direction will then beclosed 'on the car switch and the elevator will accelerate to full speedand run at that speed as long as the operator keeps the latch 204pressed against the edge 209 of notch 210.

.switchis in position 2.

The principles of operation of slow-down controller 18 will beunderstood from the diagrammatic illustration shown in Figure 2, and apractical construction will be described later in connection withFigures 3 and 4. Two parallel strips 250 and 251 are mounted in such amanner that they will move together longitudinally in accordance withthe movements of the elevator. Strip 250 is made up of a metallicportion 95, an insulatingportion 252, and a second metallic portion 253.The insulatin portion 252 is located at the point midwayiietween the twoends of the strip. Strip 251 consists of a metallic portion 254extending from one end toward the middle and another metallic portion255 extending from the other end toward the middle. At definitedistances from the center are mounted contacts 256 and 257 which areinsulated from each other and from the strip 251 by insulators 258, 259and 260. Contact 93 is located at the center otthe strip and is of adefinite length. Contacts 2G1 and 262 are similarly arranged on theother end of strip 251. Strips 250 and 251 are insulated from each otherand from the mechanism that moves them. \Vhen the elevator is ascending,the strips move in the direction of the arrowdesignated up. Posts 263,264 and 265 are mounted in fixed positions along the path of motion ofthe strips at intervals corresponding to the distance between landings.Each otthese posts, as indicated at post 263, is provided with twobrushes 266 and 267 which contact respectively with strips 250 and 251.The two brushes and post form'a conducting bridge from one strip to theother and each set is insulated from the others.

lVith the elevator ascending at full speed and approaching the landingcorresponding to post 263, at which it is desired to stop, the operatorpermits or causes the car switch to move from position 3 to position 2.The elevator will continue to run at full speed since the directionswitch and high speed switch are still in until contact 256 on strip251' comes under brush 267. Under the conditions just described,contacts 269 and 270 will be closed, due to the setting of centrifugalgovernor 22, which is driven from the elevator mechanism. Governor 22 isso set that contacts 269, 270 close when the elevator is nearly up tofull speed and remain closed until the speed hasdropped a small amountbelow full speed. A circuit will then be established from main 34through Wires 39, 49 and 50, contacts 47, 46 and 74, wire 75, resistance88, wire 89, .solenoid winding 90, wires 91, 268, contacts 269. 270,wire 271, contact 256, brushes 267, 266, strip section 95, brush 272,which is mounted to contact on strip 250, wire 96, contacts 97, 98 andwires 99, 72, 73 and 42 back to main 33. Thus the high speed switchsolenoid is energized by the current flowing in this circuit as well asby that flowing in the circuit of which solenoid winding 78 forms apart. Vinding 90, however, is wound in the reverse sense to winding 78so that the effects of the two windings are neutralized and the highspeed switch will open. As previously described. the generator voltagewill immediately decrease and the elevator motor will be retarded by thedynamic braking action of the generator until it has reached the lowspeed corresponding to the low generator voltage.

Contact 256 is placed in strip 251 in such position that it will comeunder brush 267 at a time when the elevator is distant from the landing,the minimum required to brin the elevator from full speed to low speedlit] open. Elevator motor is thereby discon-- nected from the generatorand resistance-81 is connected across the armature terminals of motor 10by the closing of contacts 124, 125. At the same time, solenoid 115 ofelectromechanical brake 16 is deenergized and the brake is applied. Inorder to provide a quicker action of the electromechanical sition 2until brake in automatically stopping, resistance 150 may be dividedinto two sections, one of which is normally short-circuited by contacts287, 288 of the magnetic stopping switch 28 through wires 286 and 289.\Vhen the arm 64 comes-opposite armature 31, contacts 287, 288 areopened and the resistance across coil 115 is increased, thereby applyingthe brake in less time.

The elevator will now be at rest with its floor approximately level withthe landing and the operator may place the car switch handle in neutralposition or leave it in pohe desires to move the elevator car again.

Considering now the case in which the elevator is running at saythree-quarters full speed and it is desired to stop at a landing:fiuch'a case might be where the elevator is proceeding from one floor tothe second floor above. The operator will place the car switch handle inposition 2, and if the elevator is accelerating it will continue to doso,-as full'speed conditions in the control circuits still obtain. 'Asthe elevator is not up to full speed, contacts 269, 270 con-,

trolled by the centrifugal governor willnot be closed and contact 256 ofthe slow-down controller will pass under brush 267 without causing anychange. Contacts 273, 274, however, are adjusted so that they will beclosed by the governor 22 when the elevator is running at three-quartersfull speed. Consequently the elevator will continue toward the landing,and strips 250 and 251 of the slow-down controller will continue towardpost 263. \Vhen contact 257- comes under brush 267, the circuit throughcontacts 274, 273 and solenoid winding will be closed and the high speedswitch will be opened. It is to be noted that the slow-down in this caseis initiated at a time when the elevator is nearer the landing than inthe case where the elevator was running at full speed. The

distance from the landing at which slow down is initiated is controlledby the location of contact 257 in strip 251 and is de- 'ing the carswitch in neutral position, the

operator will move it to position 3 and immediately return it toposition 2. Although the control circuits will be set for full speedoperation, it is unlikely that the elevator will-reach full speed and itis probable that the speed will be below threequarters full speed.Strips 250 and 251 of the floor controller will, therefore, move inaccordance 'the governor and operates to initiate auto- .to slow speed,as in the previous cases. Al-

through I have shown but three contacts in the slow-down controllercorresponding to three elevator speeds, it is apparent that any othernumber may be used under the same principles of operation.

In all cases when the elevator is brought to rest at a landing, the postcorresponding to that particular landing will be central with insulatingblock 252 and contact 93. In Figure 2, post 264 is so shown. Insulatingblockv 252 is shorter than contact 93 so that in slowing down a circuitmay be made from contact 93 through the bridge contacts of the posts toportion 95 or 253 of strip 250. Insulating block 252, however, servesthe purpose of keeping the circuit through solenoid winding 90 of thehigh speed switch open at the time of starting the elevator from alanding, so that. high speed operating conditions may be initiatedinin'iediately on bringing the car switch to full speed position.

I have found that vin stopping a certain elevator from a full speed ofsix hundred loo I feet per minute by means of my automatic lamilingprevious to the landing at which he desires to stop, in which toinitiate the automatic stint-clown and'in addition a distance above theprevious landing equivalent to one-half the length of insulating block252 which may also be about three feet. If he moves the car switch toposition 2 at any point within this six foot zone, he will make aperfect stop in a minimum of time. This is of great advantage over thecontrolling means heretofore in common use where it has been necessaryfor the operator to initiate the stopping at a definite dista-nce -itromthe landing in order to have the car come to rest exactly at thelanding, without the use of levelling devices.

lVhether-the system is provided with an automatic stop or a manuallycontrolled stop, the automatic slow-down represents an importantimprovement in the operation of elevators. It is peculiarlyadvantageous, however, in connection with an automatic stop, as will beapparent, and I regard the combination as a specific subject ofinvention in addition to the broad principles of the automatic slow-downper se.

It the operator desires-to stop the elevator at any time, whether at alanding or between landings, without utilizing the automatic slow-downand stop, he may do so by placing the car switch handle in the neutralposition in which the automatic slow-down and stop are cut out. Theelevator will then he brought to rest by the dynamic brake andelectromechanical brake as though the automatic slow-down were notpresent.

Under certain conditions of operation, I may use push-buttons 300 and301 to move the elevator for short distances at low speed. These aremounted immediately over the car switch in the elevator car. Push-button300 is for up motion and push-button 301 for down motion, and they aremechanically interlocked by mounting one on each end of lever 302 sothat both cannot be used at the same time. A contact 303 is provided onswitch handle 45, but insulated from it, and is adapted to contact witha contact 304 (mounted on the car switch) when the handle 4.5 is in theneutral position. By pressing push-button 300, a circuit is closed frommain 3st through wires 39, 49, 305, contacts 303. 304. wire 306,contacts 307, 308, 309, wires 102, 70,.solenoid 71 of the up dircctionswitch and wires 72, 73 and 42 to main 33. The direction switch willclose, brake it; will be released and the elevator will ascend at lowspeed as long as the operator keeps pressure on push-button 300.

It will be understood that down motion, both hy-the push-button 301 andbythe car switch 32 in connection with the slow-down controller andmagnetic stopping switch, is controlled in an exactly similar manner tothat described for up motion.

sprocket or gear 339 and plate 34.0. Drum 341 is driven by In Figure 3,showii-ig one form of slowdown controller, atrame-325 supports a shaft326, which is kept from turning by set screw 32? and key 328. A worm 329is fixed on the shaft 320 between the two standards of frame 323. Sliprings 330, 331 and 332 are also secured to shaft 326. These slipri'ngsare insulated from each other and from their supporting member333. Spider 334 is rotatably mounted -on shal't 326 and in bearing Thehub :36 oi spider 334 extends through bearing 335 and is driven bythrough bolts 338 and not studs 34:2 and 3 :3 which are secured inspider 334 and pass through holes in spokes to -cure ot the ring 349.hen located they are locked in place by bolts 35 fh-"" Posts 355. 350and 357 are mountedfol-lengthwise adjustment respectively in arms 351,352 and 353. (tn the outer cylindrical surface of drum 3-11" are mountedthe strips 250 and of Figure 2 in the form of a helix having the samepitch as the worm 329. The strips are insulated from the drum byinsulation Brush 272 is mounted on post 355 and as shown in Figure 3.the brid e contact 94 is mounted on post'35'T. Post 306 holds the brushcorresponding to brush 272 for down motion of the elevator. It will beunderstood that posts 263 and 265 (Figure 2) are mounted in suitablerelation to post 3570a ring 3 10. It is app rent that as the drum 341rotates the brughes will be maintained on the proper strip Figure 4shows the developed surface of the drum 341 and diagrammatically theelectrical connections andarrangements of contacts for a slow-downcontroller designed for three landings. This is the conditionillustrated in Figure 2 and the same numerals are used in connectionwith Figure t. As the operation was described in detail in connectionwith Figure 2, it is thought unnecessary to repeat it. Although I havedescribed 'the slow-down controller as designed for three landings, itmay he used For any number by proportioningthe speed of the controllerto that of the/elevator so that when the elevator, moves the full lengthof the hatchway the controller .will rotate an amount that will causethe portion 05 of strip 250. to move under brush 272 from a point nearinsulating block 252-to a point cap be placed at any point in thecircuinnear its end. In designing the controller it is also necessary tolocate contacts 256, 257

and 93 in strip 251 so as to initiate slowdown at the proper distancefrom the landing.

Having described my improved system of elevator control I desire topoint out that it atfords means for maintaining the highest possibleaverage elevator speed and for do- 10 ing away with the necessity ofhighly skilledoperators. To do thisI employ automatically controlledacceleration and retardation, which can be made as rapid as desired and,in addition, I automatically determine the point at which the elevatorwill start to slow down so that regardless of its speed it will alwaysreach a prescribed low speed at approximately the same distance from thelanding. Further I automatically stop the elevator from the low speedapproximately level with the landing without over-running.

My control system enables the operator to select, while the car is inmotion, the landing at which he desires to automatically stop and he hasquite a range of distancein which to manipulate the car switch toaccomplish this. Consequently his skill is not constantly taxed nor doeshe become so quickly fatigued.

I have found that in bringing elevators to rest, there is some variationin the distance required to stop them from any given speed, depending onthe load in the elevator. The same considerations apply in bringing anelevator from any given speed to a lower speed. It is customary tocounterbalance elevators and forty percent of the full load 7 is acommon amount. Considering an ele-' vator for a maximum lifting capacityof two 4 thousand five hundred (2500) pounds, coun terbalanced fortypercent, the maximum unbalanced load when the elevator is ascendingfully loaded will be one thousand five hundred (1500) pounds, and themaximum unbalanced load when the elevator is descending light will beone thousand (1000) pounds. These amounts represent the weights theelevator motor must lift under the extreme conditions. In additionthemotor must accelerate the total mass of the elevator, counterweights,cables, etc.. and the brakes must retard these masses. Then the elevatormotoris lifting the unbalanced load,

*as when the elevator is ascending loaded or descending light, theelevator car will stop in a shorter distance after the power is turnedoff and the brakes applied. than it will stop when the unbalanced loadis being lowered by the elevator motor.

To compensate for this variation in the distance required to stop, Iprovide means for controlling the speed of the elevator so that it willbe in some direct proportion to the load on the elevator motor at bothfull and low speeds. In this way the tendency of the elevator to stop orslow down to a. definite low speed in a shorter distance underconditions of load on the elevator motor is counteracted by the tendencyto travel a greater distance due to increased speed. This isparticularly important in the low speed operation of the elevator as itis from the low speed that the elevator is brought to rest at a landing.The means I employ to give an elevator speed that will be greater as theload on the motor increases, is the impressing on the armature terminalsof the elevator motor 10 of a voltage that will be higher as the load onthe motor increases. This voltage characteristic is produced by properlydesigning the generator 5 and particularly proportioning the seriesfield 8 in reference to the separately excited field 36 to give thedesired results.

I have obtained excellent results in automatically stopping an elevatorunder different conditions of loading by means of the inventiondescribed. As an example, the greatest variation in conditions for a.particular elevator were found to be between stopping while ascendingand stop ing while descending with the elevator fillly loaded and anunbalanced loadof one thousaid five hundred (1500) pounds. Under suchconditions I was able to stop this ele- "ator from low speed within oneinch of the landing when approaching from either direction by making theprescribed low speed sixty feet per minute when the elevator wasascending and thirty-eight feet per minute when the elevator wasdescending. The voltages at the generator terminals corresponding tothese speeds were 57 and 9 respectively. With the load in the car justbalancing the counterweight, which is the average running condition,stops were made with1n oneeighth of an inch of the landing in eitherdirection and the voltage was 34 for up motion and 32 for down motion.

This is an important improvement 1n elevator practice, where heretoforethe speed has always been slower when the motor was 11fting a load thanwhen it was retarding it, and offers many advantages in automaticcontrol, as has been pointed out.

I claim 1. An elevator system comprising, an elevator, a motor forraising and lowering the elevator, a source of curei'nt for said motor,means for automati ally initiating a reduction of the voltage of saidsource to a delinite low value to cause a reduct ion of the elevatorspeed. and means for automatically causing said definite low value ofvoltage to be in some direct proportioirto the load on said motor.

2. An elevator system. comprising, an elevator, a motor for raising andlowering the elevator, a generator for supplying current to said motor,and means for automaticall initiating a reduction of the terminal E. F.of said generator to a definite low value to cause a reduction of theelevator speedvsaid genera or having a series field winding constructedand arranged to cause said delinitelow value oi generator terminal E.llLli. to be in some direct proportion to the load on said motor.

3. An electric elevator system comprising .in combination, an elevator,a motor for' raising and lowering the elevator, a generator :forsupplying current to said motor, means for automatically determining thespeed of said motor directly in some proportion to the load thereon,said means comprising said generator, and meansffor automaticallystopping the elevator at a landing.

4. An electric elevator system comprising in combination, an elevator, amotor for raising and lowering the elevator, a. generator for supplyingcurrent to said motor, means for automatically determining the speed ofsaid motor directly in some propor tion to the load thereon, said meanscomprising said generator, and means for automatically discontinuing thesupply of current to said motor and applying a brake at a fixed distancefrom the landing to stop the elevator at the landing.

5. An electric elevator system comprising 1n combinatlon, an elevator, amotor for raising andlowering the elevator, a generator for supplyingcurrent to said motor, said generator having a series field winding, andmeans to automatically cause the elevator speed to be directly in someproportion to the unbalanced weight being lifted, said means comprisingsaid generator.

6'. An electric elevator system comprising in combination, an elevator,a motor for raising and lowering the elevator, a generator forsupplying'current to said motor, said generator having a series fieldwinding, and means to automatically cause the elevator speed to beinversely in some proportion to the unbalanced Weight being lowered,said means comprising said generator.

7. An elevator system comprising, motive means for raising and loweringthe elevator, means for automatically initiating a reduction of theelevator speed to a definite low speed at difi'erent, distances from alanding and means for causing the definite low speed i of the elevatorto be. directly in some propor- Y as tion to the load on said motivemeans.

8. An elevator system comprising, means for automatically initiating areduction of the elevator speed to a definite low speed at differentfixed distances from the desired landing, and means for causing thedefinite low speed of the elevator to be directly in some proportion tothe unbalanced weight being ifted.

9. An elevator system comprising, means for automatically initiating a.reduction of the elevator speed to a definite low speed/at difi'erentfixed distances from the desired landing, and means for causing thedefinite low speed of the elevator to be inversel in some proportion tothe unbalanced weight being lowered.

10. An elevator system comprising, motive means for raising and loweringthe elevator, means for automatically initiating a reduction of theelevator speed to a definite low speed as it approaches a selectedlanding, automatic means for rendering said initiating means effectiveat different distances from the selected landing, and means for causingsaid definite low speed to be directly in some proportion to the load onsaid motive means.

11. An elevator system comprising, motive means for raising and loweringthe elevator, means for causing the elevator to be brought from rest tofull speed, means for automatically initiatin a reduction of theelevator s eed to a de nite low s eed at a variable istance from thedesire landing,

said initiating means comprisin means for a landing for automaticallyinitiating a reduction of the elevator speed to a definite low speed ata variable distance from the selected landing, said initiating meanscomprising means responsive to the speed of the elevator for determiningsaid distance, and means for causing said definite low speed to bedirectly in some proportion to the load on said motive means.

13. An elevator system comprising, means for bringing the elevator fromrest to full speed, means rendered operative by the operator inselecting a landing -for automatically initiating slowing down of theelevator to a definite low speed at different fixed distances from thelandin selected, means for automatically determining the fixed distanceat which the initiating means becomes effective, and means toautomatically cause the definite low speed of the elevator to be directlin some proportion to the unbalanced weig t being lifted.

14:. An elevator system comprising, means for bringing the elevator fromrest to full speed, means rendered operative by the operator inselecting a landing for automatically initiating slowingdown of theelevator to a definite low speed at different fixed distances from thelanding selected, means for automatically determining the fixed distanceat which the initiat'lngmeans becomes effective, and means toautomatically cause the definite low speed of the elevator to beinversely in some proportion to the unbalanced weight being lowered.

15. An electric elevator system comprising in combination, meansnormally under control of the operator for bringing the elevator fromrest to full speed, means for automatically initiating a reduction ot.the elevator speed to definite low speed at. a distance from the desiredlanding, depending upon the momentary speed of the elevator, and meansto automatically cause the delinite low speed of the elevator to bedirectly in some proportion to the unbalanced Weight being lifted;

16. An electric elevator system comprising in combination means normallyunder control of the operator for bringing the elevator from restto'full speed, means for automatically initiating a reduction of theelevator speed to definite low speed at a distance from the desiredlanding, depending upon the momentary speed of the elevator, and meansto automatically cause the definite low speed of the elevator to beinversely in some proportion to the unbalanced weight being lowered.

17. An electric elevator system comprising in combination, meansnormally under control of the operator for bringing the elevator fromrest to full speed, means for automatically initiating a reduction ofthe elevator speed to definite low speed at a distance from the desiredlanding, depending upon the momentary speed of the elevator, and meansto automatically cause the definite low speed of the elevator to bedirectly in some proportion to the unbalanced weight being lifted'andinversely in some proportion to the unbalanced weight being lowered.

18. An electric elevator system comprising in combination, meansnormally under control of the operator for bringing the elevator fromrest to full speed. means for automatically initiating a reduction ofthe elevator speed to definite low speed at a listance from the desiredlanding. depending upon the momentary speed of the elevator, means toautomatically cause the deli- .nite low speed of the elevator to bedirectly vator from rest to full speed, means for automaticallyinitiating a reduction of the elevator speed to definite low.speed at adistance from the desired landing, depending upon the momentary speed ofthe elevator, means to automatically cause the definite low speed of theelevator to be inversely in some proportion to the unbalanced weightbeing lowered, and means for automatically initiating stopping of theelevator'at a fixed distance from a landing to bring the elevator torest approximately level with the landing. 20. An electric elevatorsystem compris ing in combination, means normally under control of theoperator for bringing the elevator from rest to full speed, means forautomatically initiating a reduction of the elevator speed to definite'low speed at a distance from the desired landing, depend ing upon-themomentary speed of the elevator, means to automatically cause thedefinite low speed of the elevator to be directly in some proportion tothe unbalanced weight being lifted and inversely in some proportion tothe unbalanced weight being lowered, and means for automatically initiating stopping of the elevator at a fixed distance from a landing tostop the elevator approximately level with the landing.

GRAHAM B. GROSVENOR.

